I recently posted an answer on the Hello, World question and after posting, discovered this answer claiming to do it in 18 bytes in brainfuck. I read through it and thought that it was completely wrong and so notified the OP in the comments. We then had a bit of an argument about whether this is a valid answer but we couldn't settle it so I thought I'd post this.

Can anyone settle this debate? Surely his answer is invalid?

• The answer he posted is valid in a completely different language called SMBF, but neither the brainfuck spec nor any interpreter I am aware of operate in this way. – Zwei Apr 14 '17 at 19:12
• First of upvote one has to be sure the code run ok. Exception are languages too convoluted with no online compiler one can check – user58988 Apr 17 '17 at 17:31
• @RosLuP Agreed. In fact, the user who posts a solution should make sure his code works before posting, if he can. This user didn't even run his code in either interpreter, nor did he view the source code of the interpreter to understand how it works. All he had to do was look at the example programs on the Esolangs page to see his wouldn't work. – mbomb007 Apr 17 '17 at 21:34

# No

I believe that this is not a valid answer because according to the Esolangs Wiki, all characters other than []<>,.+- are comments and are ignored. There is no extension listed on the wiki that behaves the way the user claims.

# However

If there exists a language (SMBF as Zwei mentioned) or an interpreter that does behave that way, then it is a valid answer, but it is not a valid Brainf**k program as the user claims it to be.

# Therefore

For now, it is an invalid answer. If the user can provide an interpreter that behaves this way for either a BF variant or another similar language, then it is valid; however, if the user fails to provide a working interpreter (that was created before the challenge), then the answer is invalid and should be removed.

If a valid interpreter is created after a challenge, as @Riker said, it is still allowed as a non-competing answer, and shouldn't be deleted. If an interpreter was created specifically to address this challenge in zero or one byte(s), then it is usually not welcomed.

# However

In this case, because the Hello World challenge is catalogue challenge, there are no "non-competing" answers, so even if the intepreter were created after the challenge, it would still be perfectly fine.

# Note: Duplicate

The answer, when modified to actually work, would just be practically a duplicate of @mbomb007's answer.

The answer has since been deleted.

• Do note that if a working interpreter is made, then it's still allowed. It's non-competing of course, but still allowed to exist (and thus shouldn't be removed). – Rɪᴋᴇʀ Apr 14 '17 at 20:31
• @Riker Yes, thank you for pointing that out. I will edit that in as well. – user42649 Apr 14 '17 at 20:34
• I mean, I'd definitely downvote that though. Just saying. (a mod of SMBF to allow such answers) – Rɪᴋᴇʀ Apr 14 '17 at 20:36
• The answerer just doesn't understand how SMBF really works, nor did he test his program. I already have a valid SMBF answer on that challenge. – mbomb007 Apr 17 '17 at 21:15
• @HyperNeutrino Also, note that the user's code could never be made valid, because the spec on Esolangs shows the Hello, World! program that works on the existing interpreter, where the source code is placed to the left of the pointer. The OP didn't reverse the string or use <. If an interpreter was created, it might be a different language, since it'd be flipped. – mbomb007 Apr 17 '17 at 21:31
• If an interpreter was created, it would be fine given that 'Hello, World!' is a catalog challenge. It would not be non-competing – Blue Apr 18 '17 at 22:08
• @muddyfish Alright, thanks, I didn't notice that. :) – user42649 Apr 19 '17 at 1:13